Prevalence and outcome of activated protein C resistance in patients after peripheral arterial bypass grafts.

The association of activated protein C resistance with peripheral arterial bypass graft patency was assessed. A retrospective cohort study of consecutive first-time femoro-popliteal or femoro-distal bypasses performed in patients living within the boundaries of the Area Health Service was performed. Of 242 patients eligible for inclusion, 73 had died, nine refused to participate and 40 were lost to follow-up. Activated protein C resistance was present in nine (7.5%) of the 120 patients tested. In the study group, smoking at the time of surgery, female gender and the use of prosthetic grafts were significantly associated with graft failure on univariate Cox regression analysis, but activated protein C resistance was not. After accounting for confounders, there was a trend (P = 0.098) for activated protein C resistance to be associated with graft failure (OR 2.90, 95% CL 0.82-10.3). Patients who died or who were lost to follow-up had significantly earlier operation dates than those who remained alive or tested for activated protein C resistance. However, there was also a highly significant (P = 0.006) trend for activated protein C resistance in patients who had undergone surgery closer to the end of the study period. Six of the nine patients with activated protein C resistance underwent surgery in the last 10 months of the review period and only three activated protein C resistance patients had a graft patent for more than 8 months. The prevalence of activated protein C resistance in patients undergoing peripheral arterial bypass grafting is greater than in the general population. There was a trend for activated protein C resistance to be associated with graft failure. A significantly higher proportion of patients with activated protein C resistance was found with more recently performed surgery. The observed results could be accounted for by excess mortality in patients with activated protein C resistance. This hypothesis requires testing prospectively.